WATER TEMP

I am running a ls1 motor in a offroad car and burnned up a piston, I had it repaired my a good machanic.I just replaced 1 piston and had the cylinder ressleved. The normal water temp allways ran at 180 degrees, after the rebuild it now runs at 210 and if I run it hard it climbs to 220.I have tried burping the radiator thinking I have a air lock, but I get nowhere. Is there anything else I can try.I have not changed anything on this car since the rebuild.I still am thinking there is a airlock, Is there any special tecnique on getting the air lock out.
Thanks guys
Johnny